Re: Pointers, auto-pointers, etc.

Lance Diduck <>
Wed, 3 Dec 2008 17:53:42 CST
On Dec 1, 5:08 pm, Ulrich Eckhardt <> wrote:

Give them this sample code and ask them to improve it using std::auto_ptr.
Actually, there are lots of ways this code can be improved, and some will
be easy when touching the code anyway.

Solutions in the next days, unless anyone else wants to jump in. ;)

My version:
struct base
    virtual ~base() {}
    //two clone functions, made safe
    template<class T> std::auto_ptr<T>clone()const{
        //dynamic_cast to handle virtual base class case
        //usually optimized away
        return std::auto_ptr<T>(dynamic_cast<T*>(clone_imp()));
        return std::auto_ptr<base>(clone_imp());
//not safe to call stand-alone, not in public interface
    virtual base* clone_imp() const = 0;
struct derived1: virtual base
    base* clone_imp() const
    { return new derived1(*this); }
struct derived2: base
    base* clone_imp() const
    { return new derived2(*this); }

void foo(){
     derived2 d2;
     d2.clone();//return value still deleted
     derived1 d1;
     //std::auto_ptr<derived1> cd2(d1.clone());//does not compile
     std::auto_ptr<derived1> cd1=d1.clone<derived1>();
     //std::auto_ptr<derived2> cd2(d2.clone<derived1>());//BOOM

     std::auto_ptr<derived1> cd2(d2.clone<derived1>());


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